This invention relates to an improvement in a rectifying apparatus which rectifies the output of an A.C. generator into a direct current and supplies the direct current for the charge of a storage battery and an electric load device on a vehicle such as an automobile.
A conventional generator apparatus which accommodates an A.C. generator and rectifying devices for a vehicle has been made up, as entirely shown in FIG. 1. In FIG. 1, reference numeral 1 denotes an A.C. generator, and 2 denotes a field winding which is mounted on a rotor of the generator 1. The field winding 2 is energized from a stator section side through a slip ring unit (not shown). The rotor is driven by an automotive engine. Reference numeral 3 denotes an armature winding which is mounted on a stator of the generator 1. The armature winding, as shown, involves 3-phase windings, which induce 3-phase A.C. voltages. Reference numeral 4 denotes a first rectifying device which accommodates three sets of semiconductor rectifiers 7. The output voltage from the armature winding 3 is applied to the anode sides of the respective rectifying devices 4. Reference numeral 5 denotes a second rectifying device which accommodates three sets of semiconductor rectifiers 7. The output voltages from the armature winding 3 is applied to the cathode sides of the respective rectifying devices 5. Thus, both the first and second rectifying devices 4 and 5 full-wave-rectify the A.C. voltage output from the A.C. generator 1. Reference numeral 6 denotes a third rectifying device which accommodates three sets of semiconductor rectifiers 7, which are connected in parallel with the rectifying device 4 with respect to a storage battery 10. The third rectifying device is used as an excitation power source for the A.C. generator 1. These respective rectifiers 7 are installed in a bracket (not shown) of the generator 1. Reference numeral 8 denotes a key switch, and 9 denotes a charge indication lamp which indicates the charging state of the generator 1. The storage battery 10 is charged by the D.C. voltage output which is full-wave rectified by the rectifying devices 5 and 6. Reference numeral 11 denotes a voltage regulator which serves to maintain the output voltage of the generator 1 at a predetermined level, and 12 denotes a load switch which opens or closes a circuit of an electric load 13 from the rectifying devices 4 and 5, and the storage battery 10. Reference numeral 14 denotes a D.C. output terminal of the rectifying device 4, and 15 denotes an initial excitation terminal, 16 denotes a field winding terminal, and 17 denotes a terminal which is connected to an automotive body.
In the conventional generator apparatus described above, the result of the D.C. output from the generator apparatus in the state of spectral analysis in the frequency range of 0 to 2 MHz is shown in FIG. 2. In FIG. 2, it is understood that noise of approx. -60 to -40 dB has been involved in the above D.C. output in the frequency range of 0 to 2 MHz. Such noise which is thus contained in the above-described frequency band is detrimental for a radio transmitter/receiver.
In order to remove such noise components in the D.C. output of the conventional generator apparatus, another example of a generator apparatus has been made up, as shown in FIG. 3. This example has substantially equal arrangements to the circuit arrangement shown in FIG. 1, but a capacitor 18 which accommodates a capacity of 0.5 to 2 .mu.F is connected between the D.C. output terminal 14 and an automotive body to absorb and reduce the noise which has been produced from the rectifying devices 4 and 5.
FIGS. 4 and 5 show the results of the D.C. output from this example of the conventional generator apparatus in FIG. 3 in the state of spectral analysis in the frequency range of 0 to 2 MHz in terms of capacitors accommodating capacities of 0.5 and 2 .mu.F, respectively.
From FIG. 4, showing in case of the capacitor 18 having 0.5 .mu.F, it is understood that most noise has been removed as compared with the result shown in FIG. 2 in case of no capacitor connected. However, this result still shows noise in the range of 100 kHz which has not yet been sufficiently removed and therefore remains.
From FIG. 5, showing in case of the capacitor 18 having 2 .mu.F, it is understood that the noise remaining in the vicinity of 100 kHz has almost been completely removed, and the noise level has also been reduced to approx. -70 dB, which causes almost no problem in a practical use.
In the conventional generator apparatus described above, a capacitor which accommodates a relatively large capacity is required so as to completely remove the noise which has been produced from the rectifying devices 4 and 5. It is thus necessary to involve a capacitor which has a capacity of as low as 0.5 .mu.F in the generator apparatus so as to remove the noise to a certain degree, and this accordingly results in a high cost and complicated works in the installation of the capacitor.